Keyway shutters for cylinder locks



Sept. 29, 1959 c. A. VAHLSTROM KEYWAY SHUTTERS FOR CYLINDER LOCKS FiledDec. 18. 1956 INVEN TOR. ('HRL fl. Vii/ 187F007 KEYWAY SHUTTERS FORCYLINDER LOCKS Carl A. Vahlstrom, New Britain, Conn., assignor to TheAmerican Hardware Corporation, New Britain, Conn, a corporation ofConnecticut Application December 18, 1956, Serial No. 629,049

Claims. (Cl. 70-455) This invention relates generally to key operatedcylinder locks, and more particularly to shutter means for sealing thekeyway of such locks against the entry of dirt and moisture.

Locks of the type for which this invention is particularly intendedcomprise a lock housing having a bore in which a key plug is mounted torotate. The key plug contains an axially extending keyway which opens toits periphery and is normally prevented from rotating by a plurality oftumbler elements which are movable to an ineffective position uponinsertion of a proper key into the keyway to free the key plug forrotation.

Many different types of keyway shutters have heretofore been devised,but all known prior devices have either been attached to the exterior ofthe housing or the key plug or have required the use of exteriorelements of one type or another for retaining the shutter member ormembers in position. Such exteriorly attached elements increased thecost of the locks and, in some cases, prevented their use on deviceswhere a lock having a keyway shutter was desired. This was particularlytrue in the case of door locks requiring a cylinder lock in the outerknob thereof where the particular manner in which the cylinder look wasinstalled in the knob did not permit the use of exterior attachments onthe housing or the key plug and therefore prevented the use of keywayshutters in such applications.

The primary object of the present invention, therefore, is to provide acylinder lock having shutter means for the keyway carried internally ofthe key plug and which require no exterior attaching means of any kindfor retaining the shutter elements therein.

A further object of the present invention is to provide keyway shuttermeans for a cylinder lock which in no way affect the external dimensionsof the lock or its appearance and are, therefore, particularly adaptedfor use in cylinder locks used in the outer knobs of door locks and thelike.

Another object of this invention is to provide keyway shutter meanswhich may be adapted to many different types of cylinder locks withoutrequiring extensive modification thereof.

A still further object of the invention is to provide keyway shuttermeans which are particularly adapted for use in cylinder locks in whichthe keyway in the key plug opens to the periphery of the plug.

A still further object of the present invention is to provide keywayshutter means for a cylinder lock which are constructed in a novelmanner and are inexpensive to produce.

Further objects and advantages of the present invention will be moreclearly understood from the following description and the accompanyingdrawing in which:

Fig. 1 is an end view of a cylinder lock embodying my novel shuttermeans.

Fig. 2 is' a side view thereof, partially in central vertical section,further illustrating said shutter means.

Fig. 3 is an enlarged end view of the lock taken in vertical section online 33 of Fig. 2 and illustrating the keyway shutters in closedposition.

Fig. 4 is a sectional bottom view taken substantially on line 4--4 ofFig. 3.

Fig. 5 is a view similar to Fig. 3, but showing the shutters in openposition and a key in the keyway of the lock.

Fig. 6 is an end view of the key plug partially in vertical section.

Fig. 7 is a fragmentary view of said key plug.

The cylinder lock in which I have chosen to illustrate my invention isof a conventional pin tumbler type and is particularly adapted for usein the outer knobs of door locks, but it will be readily understood fromthis disclosure that my invention is applicable to many other types ofcylinder locks.

The cylinder lock includes a cylindrical housing 5 having a pin tumblerchamber 6 extending radially therefrom. The housing 5 is provided withan axial bore 7 in which a cylindrical key plug 8 is mounted to rotate.In the particular lock shown, the key plug 8 is provided ,at its outerend with a flange 9' providing an annular shoulder 10 on the plug whichengages the end of the housing 5 and prevents axial movement of the pluginwardly relatively thereto. The key plug extends through the bore inthe housing and is retained against outward axial movement with respectthereto by a suitable C-ring 11, and the inner end of the key plugcarries an axially extending blade 12 which is attachable to themechanism ,controlled by the cylinder lock. The key plug contains anaxially extending keyway 13 which opens to the front of the flange 9 andalong one side of the plug and said plug is normally prevented fromrotating by a plurality of pin tumblers 14 which are slidable innormally aligned radial openings in the chamber 6 and the key plug andare urged into locking position, fas illustrated in Fig. 2, by tumblersprings as shown at 15. The tumblers 14 are shifted into shear positionpermitting rotation of the key plug upon insertion of the proper keyinto the keyway 13.

Since it is desirable to prevent the entry of foreign matter into thekeyway, I have provided novel keyway shutters for closing that portionof the keyway located in the bore of the housing and containing thetumbler mechanism. In accordance with my invention, a portion of the keyplug directly behind the shoulder 10 on the flange is cut away toprovide a transverse slot 16 therein which opens around the oppositesides and bottom of the peripheral surface of the key plug. The slotextends across the keyway, as best shown in Figs. 3, 5 and 6, and is cutin such a manner that its upper edge is defined by oppositely inclinedsurfaces 16a-16a which extend from opposed points on the periphery ofthe plug toward the edge of the keyway and meet at the center of the keyplug at a point above said edge. It will be noted from Figs. 2 and 4that the slot 16 is disposed entirely within the bore 7 so that theopening around the periphery of the key plug is closed by the wall ofthe bore.

Prior to the formation of the slot 16, opposed transverse holes aredrilled into the key plug on the opposite sides of the keyway atpredetermined angles corresponding to the angles of the edge portions.16a--1 6a of the slot, and said holes preferably open into the keyway.The holes are drilled on axes located substantially at the predeterminedcenter of the slot and are larger than the slot so that after said slotis formed, its opposite walls contain opposed recesses 1717 at oppositesides of the keyway which extend parallel to the adjacent edge portions16a16a; the recesses in the front wall of the slot extending outwardlyto the periphery of the flange 9."

Within the slot 16, there is contained a pair of opposed transverselyslidable shutter plates il818, one ateach side of the keyway, havinginner edge portions 18a-18a adapted to meet at the center of the keywayand thereby close the keyway. The shutter plates are preferably bevelledalong their meeting edges to provide forwardly facing cam surfaces18b18b and the outer edges of said shutter plates are curved on a radiusconforming substantially to the radius of the key plug. Each of saidshutter plates contains an angular lydisposed notch 19 which extendsinwardly from its outer edge and is aligned with the adjacent recesses1717 to accommodate a compression spring which is disposed in saidrecesses and acts between the inner edge of the notch and the wall ofthe bore in the housing 5. The springs 2020 urge the shutter plates intoclosed position and also exert a downward force thereon to maintaintheir lower ends against the wall of said bore, as illustrated in Fig.3. It will also be noted from Fig. 3 that the upper edges of the shutterplates extend parallel to the notches 19-19 and to the adjacent edgeportions 16a16a of the slot 16.

When the proper key, indicated at 21, is inserted into the keyway, theshutter plates 18-48 will be forced apart upon engagement of the end ofthe key with the cam surfaces 18b18b to allow passage of the key intothe portion of the keyway rearwardly of said slot. As the shutter platesmove apart, the lower edges slide along the wall of the bore and theresulting movement of the plates is therefore angular. The angle ofinclination of the upper edges 16a16a of the slot 16, the upper edges ofthe plates 1818, the recesses 17-17 and the notches 1919 correspond tothe angle of movement of the plates, and it will therefore be understoodthat the springs 20-20 are axially compressed as the said shutter platesare moved to open position, as illustrated in Fig. 5. If desired, theend of the key can be bevelled to provide cam surfaces on its oppositesides which engage the cam surfaces 18b18b to facilitate spreading ofthe shutter plates.

When the key is withdrawn from the keyway, the springs 2020 will movethe shutter plates angularly into closed position. The lower edges ofsaid plates are always maintained against the wall of the bore by thesprings and it will therefore be understood that my novel shutter meansis particularly useful in cylinder locks wherein the keyway opens to theperiphery of the key plug.

I claim:

1. A cylinder lock comprising a lock housing having a bore, a key plugmounted to rotate in said bore and having an axially extending keywayopening to its front end and along its periphery, said key plug having atransverse slot therein opening around its periphery from the oppositesides of said keyway and extending across the entire keyway, said slotbeing disposed entirely within said bore, a pair of opposed shutterplates contained within said slot and having meeting edge portionsadapted to close said keyway, the lower end portions of said shutterplates being slidable upon the wall of the bore whereby said plates areguided for angular movement in opposite directions between positionsclosing and opening said keyway, and a pair of springs contained withinsaid slot, one acting between each of said shutter plates and theadjacent wall of the bore and normally biasing said plates into keywayclosing position each of said springs being so disposed that the forceexerted thereby is applied to its respective shutter plate in adirection substantially parallel to the direction of movement of saidshutter plate thereby to press the said lower end portion of the shutterplate against the wall of the bore.

2. A cylinder lock comprising a lock housing having a bore opening toits front end, a key plug mounted to rotate in said bore and having aflange on its front end providing an annular shoulder abutting themarginal edge portion of said bore at the front end of said housing,said key plug having an axially extending keyway opening to its frontend and along its periphery and a transverse slot extending rearwardlyfrom said shoulder and across the entire keyway, said slot openingaround the periphery of the key plug from the opposite sides of thekeyway and being disposed entirely within said bore, a pair of opposedtransversely slidable shutter plates contained within said slot andhaving meeting edge portions adapted to close said keyway, the loweredges of said shutter plates being slidable on the wall of the borewhereby said plates are guided for angular movement between closed andopened positions, said shutter plates having notches extending inwardlyfrom their outer edges at an angle corresponding to their angle ofmovement, and the opposite walls of said slot having opposed recessesaligned with said notches and extending inwardly from the peripheralsurface of the key plug, a compression spring disposed in the recessesat each side of said key plug and in the notch in the adjacent shutterplate and acting between the bottom of its respective notch and theadjacent wall of the bore to normally bias the shutter plate into keywayclosing position, said springs maintaining the lower edges of saidshutter plates in engagement with said wall.

3. In a key operated cylinder lock, a housing having a circular bore, akey plug mounted to rotate in said bore and having an axial keywayopening to its front end and along its periphery, said key plug having atransverse slot therein disposed in said bore, a pair of opposed shutterplates movable in said slot and having meeting edge portions adapted toclose said keyway, the ends of said shutter plates adjacent theperiphery of the key plug being slidable on the wall of the bore andguided thereby for angular movement in opposite directions betweenpositions closing and opening said keyway, the edge of said slot beingV-shaped with the two surfaces thus formed extending from a point abovethe center of the keyway to the periphery of the key plug substantiallyparallel to the direction of movement of the adjacent shutter plate, andspring means in said slot normally yieldably maintaining said shutterplates in keyway closing position.

4. In a key operated cylinder lock, a housing having a circular bore, akey plug mounted to rotate in said bore and having an axial keywayopening to its front end, said key plug having a transverse slot thereindisposed in said bore and extending across the entire keyway, a pair ofopposed shutter plates slidable in said slot and having meeting edgeportions adapted to close said keyway, a compression spring in said slotacting between each of said shutter plates and the wall of said bore andnormally yieldably maintaining said shutter plates in keyway closingposition, the walls of said slot having opposed recesses extendinginwardly from the periphery of the key plug for receiving said springswhereby said springs are prevented from bending during rotation of saidkey plug.

5. In a key operated cylinder look, a lock housing having a bore, a keyplug mounted to rotate in said bore and having an axial keyway openingto its front end, said key plug having a transverse slot thereinextending across the entire keyway and disposed in said bore, a pair ofopposed shutter plates slidable in said slot and having meeting inneredge portions adapted to close said keyway when in abutting relation,each of said shutter plates having a notch extending inwardly thereintofrom its outer edge, and an elongated, coil, compression spring disposedin each of said notches and acting between the bottom thereof and thewall of the bore to normally yieldingly maintain said shutter plates inkeyway closing position.

References Cited in the file of this patent UNITED STATES PATENTS1,560,868 Shinn Nov. 10, 1925 1,965,942 Jacobi July 10, 1934 FOREIGNPATENTS 593,540 Germany Feb. 27, 1934 638,078 France Feb. 14, 1928

